Objectives

We will evaluate two preserved arthropods (grasshopper and crayfish), look for similarities in these two animals that may be phylum traits, and look for differences in the two that may be class traits.

Background Information: The Crayfish

Life Cycle of Crayfish

The life cycle of the crayfish starts with the egg. The egg is attached to the tail of the female and when the eggs hatch they are fully formed. The crayfish stays with the mother for one to two weeks and then separate from its mother. It takes about three to four months for it to reach adult size and the lifespan of the crayfish is three to eight years.

Crayfish kills

The killers of Crayfish all over the world are plentiful! They range anywhere between snakes to raccoons to human beings.

Living as a Crayfish

Crayfish are nocturnal, they frequently live underneath rocks and are found in any water that is not too polluted. Crayfish are omnivorous and also scavengers. They dine on many creatures including some insects, worms, frogs, toads, and more!

Life Cycle of Crayfish

The life cycle of the crayfish starts with the egg. The egg is attached to the tail of the female and when the eggs hatch they are fully formed. The crayfish stays with the mother for one to two weeks and then separate from its mother. It takes about three to four months for it to reach adult size and the lifespan of the crayfish is three to eight years.

Crayfish kills

The killers of Crayfish all over the world are plentiful! They range anywhere between snakes to raccoons to human beings.

Living as a Crayfish

Crayfish are nocturnal, they frequently live underneath rocks and are found in any water that is not too polluted. Crayfish are omnivorous and also scavengers. They dine on many creatures including some insects, worms, frogs, toads, and more!

Arthropods and the Integuentary System

Arthropods have hard shell made of calcium carbonate secreted by the mantle, a heavy fold of tissue that surrounds the mollusc's internal organs. Spiders, insects, lobsters, and shrimp, have bodies covered by an external skeleton, the exoskeleton, which is strong, impermeable, and allows some arthropods to live on land. The exoskeleton is composed of layers of protein and a tough polysaccharide called chitin, and can be a thick hard armor or a flexible paper-thin covering. Arthropods grow by shedding their exoskeletons and secreting a larger one in a process called molting.

Since the exoskeleton of an arthropod is a rigid structure, it must be shed and replaced periodically to enable growth. This shedding process is known as molting or ecdysis and consists of a series of four stages. First, enzymes are secreted that loosen the old exoskeleton layers. Second, the new exoskeleton layers are secreted. Third, the old exoskeleton splits and falls off. Finally, the new exoskeleton hardens and sets.